I-Data 5250 ALLY - Manual (Page 69)

CHAPTER 3
CHARACTER CODE TRANSLATION
Overview
The data stream that is sent from the AS/400, System/3X or alternate host
device is not forwarded directly through the AGILE 5250 ALLY to the
printer. Rather, all characters must first pass through the appropriate
character code translation table.
If the data format that the printer uses is the same as the format in which
the source device sends data, then the data should be routed through a
pass-through table (either ASCII to ASCII or EBCDIC to EBCDIC). If the
data formats of the two devices are different, then a translation table must
be selected that will convert the data from one format to another.
The 5250 ALLY contains sixteen tables that are used to translate character
codes. Of these, four are used by the 5250 ALLY for the four
combinations of ASCII/EBCDIC to/from ASCII/EBCDIC. Four are used
for specialized printer applications. One table is used to convert Xerox
EBCDIC characters into ASCII format during downloading from the host.
The other seven tables are user configurable for translation to nonstandard
character sets, international use, etc.
Each table has 256 values that are used to translate an input value to an
output value. Both the input value and the output value are a single byte,
i.e., two hexadecimal digits. Each table is organized as 16 rows of 16
values each, which makes it easy to look up the output for any input.
(These tables are sometimes called “lookup” tables.)
The most basic function of the 5250 ALLY is to convert EBCDIC SCS
(twinax host) data to ASCII data one byte at a time. When a character is
received by the 5250 ALLY, the corresponding character from the selected
translation table is substituted, and that value is sent to the printer.
The tables are listed and described here along with their hexadecimal
access numbers: